Perennial, tufted grass from fibrous roots, semi-rhizomatous; stems stout, erect, 200-300 cm tall.
Sheaths smooth, loose, twisting in the wind and aligning the blades on one side; blades flat, mostly 20-40 cm long, 10-40 mm wide, usually breaking from the stems by winter; ligules half membrane and half hairs, the innovations mostly membranous, the fringe of hairs late in developing, 1.5-3 mm long.
Inflorescence a large feathery panicle, 15-35 cm long, often purplish, but later straw-coloured; spikelets generally 3- to 6-flowered, 10-15 mm long; lower glumes 4-6 mm long, the upper ones about 6-9 mm long; lower lemmas hairy, unawned, 9-12 mm long, the upper ones generally smaller but with awns often as long as the bodies, smooth, but exceeded by the silky hairs of the rachillas; paleas scarcely half as long as the lemmas; lodicules scarcely 1 mm long; anthers about 2 mm long.
The following publication provides field characters and a key for separating subspecies of North American Phragmites:
Swearingen, J. and K. Saltonstall. 2010. Phragmites Field Guide: Distinguishing Native and Exotic Forms of Common Reed (Phragmites australis) in the United States. Plant Conservation Alliance, Weeds Gone Wild. Available Online.
Additional sources provide tips for separating the subspecies, most of which use the same traits: glume length, culm/stem colour, leaf colour, habit. These include: Catling (2007), Martin (2003), Blossey (2002)
Read the Plant Conservation Alliance page for further information on how to separate the native and introduced types.
Read the Invasive Plant Network page on how to separate the two subspecies.
Blossey, B. 2002. Replacement of native North American Phragmites australis by introduced invasive genotypes.BEN - Botanical Electronic News 284
Catling, P. M. 2005. New "top of the list" invasive plants of natural habitats in Canada. BEN - Botanical Electronic News 345.
Catling, P. M. 2007. Canadian Phragmites database – notes for use. BEN - Botanical Electronic News 370
Martin, M. 2003. Common Reed (Phragmites australis) in the Okanagan Valley, British Columbia, Canada. BEN - Botanical Electronic News 318
Myerson, Laura A., David V. Viola and Rebecca N. Brown. 2009. Hybridization of invasive Phragmites australis with a native subspecies in North America. Biological Invasions 12 (1): 103-111.
Mozdzer, Thomas J. and Joseph C. Zieman. 2010. Ecophysiological differences between genetic lineages facilitate the invasion of non-native Phragmites australis in North American Atlantic coast wetlands. Journal of Ecology 98 (2): 451 - 458.
Snyder, Eric. 2009. Invasive common reed (Phragmites australis (Cav.) Trin. ex Steud subsp. australis): first record for Manitoba and the Canadian prairies. Botanical Electronic News #418, December 3, 2009.
USDA. 2010. Plant profile for Phragmites australis. United States Department of Agriculture. Available Online.